Remember that iMovie will also work with the still photos that you have. One thing that I've done is taken my vacation photos (Disney Cruise, etc), bring them into iMovie as stills, add effects to them (Ken Burns, etc.), add a soundtrack and export the whole mess to iDvd. Makes a spectacular presentation that you can view on your TV. Or make gifts of the DVD's for your friends!
With your space pictures, I can imagine some unbelievable movies and DVD's.
Tom (... I just LOVE this stuff)